With advantages of energy saving, environmental protection and long service life, light emitting diodes are widely applied in fields like LCD backlight, outdoor display, landscape lighting and general lighting. At present, most blue- and green-light-emitting devices are nitride-based semiconductors, whose epitaxial growth mainly is divided into homoepitaxial growth and heteroepitaxial growth. In homoepitaxial growth, a substrate with lattice match of the nitride-based semiconductor is used, such as a GaN substrate; and in heteroepitaxial growth, a substrate with lattice mismatch of the nitride-based semiconductor lattice is used, such as a sapphire substrate or a Si substrate.
As substrates with homoepitaxial growth are generally higher-cost, most substrates are formed via heteroepitaxial growth. However, given the considerable crystal lattice stress between the heterogeneous substrate and the nitride-based semiconductor layer, in current process, a low-temperature GaN (AlGaN) non-lattice layer is formed on the substrate, and a high-quality GaN layer is then formed to gradually eliminate defects caused by the stress. However, the epitaxial structure formed in this way remains as high as 1×108-1×1010 cm−2 defect concentration and causes carrier leakage and increasing non-radiative recombination centers, thereby decreasing internal quantum efficiency (IQE) of the device.